High-frequency ignition system



Patented Feb. 2, 1954 HIGH-FREQUENCY IGNITION SYSTEM Kenneth A. Harmon, Longmeadow, Mass., as-

signer to Wico Electric CompanmrWest Spring- Held, Mass., a corporation of Massachusetts Application March 13, 1951, SerialNo. 215,360

This invention. relates to improvements in ignition systems for internal combustion engines and, more particularly, to systems of the general type in which the ignition are produced discharges from a condenser. The improvements re late primarily to the ineens for charging the condenser.

In systems of this character, engine-driven alternator has been used, operating through a inll\vave rectifier to charge trae condenser. These generators can be designed to function setisiactorily over normal Working speeds of the enf ne. Thediiculty to produce adequate ignition dure ing the relatively slow starting speeds espe" ally under unfavorable conditions, such cold weather and a partly depleted battery, Ea :y operated induction coils have 1eeen for the purpose but these are not effective et the field Winding of the generator during starting intervals to produce in suoli winding a current pulsating at high ire nene-y, while the field mage net is temporarily rendered ineffective for its normal function, whereby to induce in the arrnature winding the currents necessary for adequate charging of the condenser.

The invention has for another object the control of the vibrator by the saine means that controls the starting niotor of tiie engine so that tlie generator is made to function like a transformer during each starting interval and as a generator during all'otlier intervals of operation.

As contrasted with a generator and cattery-operated induction coil used alternately during normal and starting intervals, respectively, of engine operation, this invention uses the one generator,

making it function in the normal manner, during normal intervals ci engine operation, and disabling it during starting intervals of operation from functioning in the normal manner and uti* lizing; its field and armature windings and niagnetic structure as a transformer.

The invention is disclosed for illustrative purposes in the accompanying drawing, in which,

The figure is an electrical diagram of an ignition system embodying the invention.

Referrinfto the drawing; the ignition system,

1 Claim. (Cl. S22-70) in general, includes an alternating,r current gencrater l, adapted to be suitably driven by, and in timed relation with, the internal combustion engine, for which the system is to supply ignition; a condenser adapted to be charged by the gen erator; a full-wave rectifier 3, interposed between the generator and condenser; a spark timer ccmprisinCr a rotary switch arm il, adapted to be driven in timed relation with the generator and engine, as by a shaft indicated diagraininatically at E, and a circular series or" contacts E, adapted to be successively engaged by arm t; spark-nlug transformers one for eacli Contact 6 and cach comprising a primary l and a secondary ii; and spark plugs 9 one for each contact and engine cylinder.

The generator includes, as relatively rotatable elements, a stationary armature lil and a rotatable field magnet H, cach constructed of suitable magnetic material. The elements iii and Il have a circular series o'radial cores l2 and I3, respectively, equally spaced one from another by a predetermined angle. The rotor l i is driven by shaft in suitable timed relation with the engine (in this case at half engine speed). The number of cores on each element is equal to the number of cylinders in the engine or some multiple of the number of cylinders. On each core i2 is a coil lil and the several coils are connected together in series so that the voltages in each are added, the Whole forming an armature winding. The ro tary ield magnet is electrically excited and for this purpose is jirovided with an exciting windn ing composed of a plurality oi coils 5, one on each core i3, and electrically connected in Series.

The terminals of the exciting Winding are 1" spectively connected by Wires i5 and il to slip rings it* and IQ, which are rotated by shaft 5, and which are engaged by brushes Z5 and 2i, respectively. Brush 2i is connected by a wire 22 movable magnetic arm 23 of a vibrator 24. This arm il@ carries a contact 25 which is en caged with a stationary contact The latter is connected by a Wire 2l to the ground. Bridged across tliesemaize and break contacts 2t and 26 is a condenser 2t. The other 'crush 2Q is connected tyk a Wire 2t to a fuse til and the latter is connected by a Wire 3l to one terminal of a manually-operated ignition switch 52, which in turn is connected by a wire 33 to one terminal a storage battery 5t, the other terminal of which is grounded. The make and break contacts 25 and 26 are always engaged when the vibrator 25 is not in operation. Thus, on c1os ingof the ignition switch 32, a current from are connected by wires 4I and i2 to the condenser 2. The output terminal 39 is grounded. The output terminal lll is connected by a wire 43 to the rotatable switch arm Each contact 6 is connected by a wire te to one terminal of the primary of a spark plug transformer. The other terminal of the primary l is grounded. Thus, whenever the arm fi engages a contact S a circuit is completed from the condenser 2 through the primary i, whereby to induce a high voltage current in the secondary 8, the terminals of which are connected in the usual, or any suitable manner, to a spark plug 9.

The vibrator 3ft includes in addition to the make and break contacts and 2t, an electromagnet having a core and coil et arranged,

whenever this coil is energized, to attract the resilient magnetic arm 23 and move it to disengage contact 25 from Contact 2d. An energizing circuit for the electromagnet is provided and may be traced as follows, from one terminal of It' battery 34, wire 33, a wire fil, the switch element 48 of a relay, wires t9 and 5t, coil liti, a wire 5I, arm 23, contacts 25 and 25, and wire 2l to the ground and thus to the other terminal of battery 34. Whenver the switch i8 is closed, the energizing circuit for coil G6 will be closed and the arm will be attracted by the magnetized core lli to disengage contact 25 from contact 2.6. As soon as this occurs, the circuit to coil it is broken and the contacts 25 and 26 reengage, to be subsequently reengaged and disengaged, the contacts opening and closing at a very rapid rate, say for example at the rate of 100 times per second.

The switch lill is preferably the switch that controls the motor 52 used to Start the engine or one actuated with such switch. The circuit for this motor may be traced as follows, from the ungrounded terminal of battery wires 33 and l, switch 48, wires i9 and 53 and motor 52 to the ground and thus to the other terminal of the i battery. This switch 13d is usually actuated by a relay, comprising a core 54 and coil 555. This coil, is energized from battery when a push button switch 55 is actuated. The circuit for coil 55 may be traced as follows, from the ungrounded terminal of battery 3d, a wire 5l, switch SiS, a wire 58, coil 55 and a wire 5d to the ground and thus to the other terminal of the battery. Whenever the circuit to the starting motor 52 is closed, the vibrator 2li will be actuated at high frequency to produce in the field winding a pulsating current, which produces a 'pulsating magnetic eld and induces an E. M. F. in. the armature winding. The exciting winding and neld winding then function as the primary and secondary, respectively, of a transformer.

In the normal operation of the ignition system, except when starting the engine, the condenser 2 is periodically charged by the generator I, func tioning purely as such, with a rotating field uniformly magnetized by battery current and with alternate polar ends of successive cores I3 of opposite polarity. Each alternation of the generator I is used to produce a spark. The condenser 2 receives as many charges per revolution of the eld magnet II as there are cores on the latter and on the armature Ill. The rectifier 3, by an action analagous to a check valve in a hydraulic system, prevents return flow from the condenser 2 to the generator I and thereby the charge is held in the condenser 2 until the spark timer arm 4 engages a contact 6 and allows the condenser to discharge through the primary 'I of a spark plug transformer and cause the induction of a high E. M. F. in the secondary B to produce the ignition spark at plug 9. This occurs at the low point of each alternation after time enough has been allowed for the charge to build up in the condenser. The timer arm 4 preferably makes actual engagement with each contact B. As the arm 4 approaches suiciently close to a contact 6, the gap between them is ionized and the condenser 2 will then discharge across this gap. There will be but one discharge of the condenser because the ensuing physical engagement of arm 4 and contact E will prevent further charging of the condenser. This arm 4 is the spark timing means, even though it also functions to distribute the discharges of the condenser. lt is the only means available to effect the timing.

On starting the engine, the closing of the energizing circuit to starting motor 52 also closes the energizing circuit to the coil i6 of the vibrator 24 and the latter is placed in operation, causing the contacts 25 and 26 to make and break at high frequency. This produces a pulsating current in the field winding of the generator I and induces currents in the armature winding to charge the condenser 2. During this starting interval, the generator I no longer functions in the normal way because its field magnet is temporarily disabled insofar as effective operation is concerned. In place of the constant magnetic ux theretofore produced by battery excitation at constant voltage, a pulsating flux is produced at ran extremely rapid rate and charging current may be applied several times to the condenser during the interval in which the rotor moves an angular distance equal to that between successive poles. Thus, the rotating field is rapidly interrupted and its value as a rotating iield magnet is temporarily lost. The condenser is then charged by transformer action and very effectively because of the very fact that the generator ield magnet is disabled. lf, for example, the rotary iield magnet consisted of permanent magnets, the flux from these would at times oppose the flux produced by the vibrator in the eld winding and interfere with the desired transformer action. With the arrangement of this invention, effective ux reversals at high frequency are obtained without the interference, which would be had if permanent magnets were used as the rotating iield of the generator.

Usually, the starting motor will, under optimum conditions, turn the engine at about 200 R. P. M. With a low battery, and/or in cold weather, this rate may be greatly reduced. It is generally required that effective ignition sparks be produced, when the engine is moving at as low a speed as 40 R. P. M. Since the generator turns at half engine speed, the speed limits, during which effective ignition must be produced during the starting interval, are from to 20 R. P. M. With an eight pole generator as shown, from 800 to alternations per minute would be produced or from between 13 and 14 to between 2 and 3 alternations per second. The arrangement of this invention operates, independent of engine speed, at a much higher rate, say 100 alternations per second and will produce adequate ignition even under the unfavorable very low speed conditions. Charging current will be applied to the condenser several times during the interval that the generator moves through an angle equal to that between successive poles and in which time only one charge would be produced by the generator when functioning in the normal way. The lower the speed, the greater number of times a charging current will be applied in said interval which is what is needed, because if the voltage available from the battery is low, more charging currents will be needed to offset the lowered voltage. charging currents in the interval that the generator would produce one, at an engine speed of say 200 R. P. M., and around thirty three at the low engine speed of 40 R. P. M.. Thus, the condenser may be well charged during starting intervals of engine operation because engine speed is not a factor in the generation of the E. M. F. required and the rotating field magnet of the generator is temporarily rendered ineffective for its normal function.

While the use of a full-wave rectifier is desirable and preferred because it enables all the alternating current generated during normal running operation of the engine to be utilized for condenser-charging, it is not essential to the present invention which relates primarily to the charging of the condenser, during starting intervals of operation of the engine, by means of a pulsating direct current that does not need, or depend on, a rectifier. Thus, a half-wave rectifier might be used without effecting the ignition at starting and, although this would result ing' a less efficient utilization of the generated alternating current, the lessened efficiency might be compensated for by suitable means.

The invention thus provides as a condenser charging means, an alternating current generator structure and means for utilizing this structure in two different ways, rst, as a generator of alternating current having a battery-excited field magnet producing constant magnetic flux, and second, as a transformer, the field and armature windings respectively functioning as the primary and secondary windings of the transformer and the eld magnet of the generator be ing disabled, while a high frequency pulsating current is produced in the eld winding by a vibrator.

What is claimed is: p

The combination with an alternating current j generator having relatively rotatable elements, a

, mature winding an electromotive force is generated on relative rotation of the elements, of an ',;e1ectric energizing circuit including said field AThis invention will produce around seven winding and adapted for connection to a battery, a pair of contacts in said circuit; a vibrator including said contacts, a stationary support for one contact, a resilient support for the fother contact tending to hold it engaged with the first contact, said resilient support having a magnetic armature, and an electromagnet opera` ble when energized to attract said armature and move said resilient support to disengage the contacts; an energizing circuit for the electromagnet adapted for connection to the battery in parallel with the field Winding and including in series said contacts and electromagnet, and a control switch in the last-named circuit, whereby when the control switch is closed the contacts in the iield winding circuit may be opened and closed at a constant and high frequency determined by the resiliency of the support for the movable contact and independently of the speed of relative rotation of said elements to generate lan electromotive force in the armature Winding.

` KENNETH A. I-IARMON.

References cited 1n the fue of this patent UNTTED STATES PATENTS Number Name Date 1,510,437 Bohli Sept. 30, 1924 2,012,581 Rees Aug. 27, 1935 2,149,397 Kongsted Mar. 7, 1939 2,330,431 Klotsch Sept. 28, 1943 2,433,715 Smart et al Dec. 30, 1947 

